Geeks might like "deactivate". One could, perhaps, construct "dewaken". :)However, one definition of awaken is "to cause to become awake" so we're looking for a word that means "to cause to go to sleep". so "anesthetize" comes to mind.

Neither "lull" nor "deaden" mean "fall asleep". ("Lull" means something like "to make [someone else] sleepy," although "awaken can also be used transitively to mean "to make [someone else] wake up".) The nearest counterpart to "awaken" (intransitive) that I can think of is "nod off". I can't think of a single word counterpart offhand.

Well, if we're going to make up words, then how about "awaken"? Yes, let's use awaken as the opposite of awaken. Instead of using the a- prefix as an intensifier, we can use it for negation, as in amoral, amorphous, atonal, etc. I suppose you could pronounce it differently if you really want, "uh"-waken for waking up, and "ay"-waken for going to sleep.

Or maybe we should use "asleepen" instead. Why not? there's wake and sleep, awake and asleep, so why not awaken and asleepen? If asleepen sounds funny or awkward, isn't awaken just as much so? It's construction is similar.

"Nod off" seems correct. Doze off could be another... but it seems the question is to find a word, not a composite one, right? Hmmm... "slumbered"? "he slumbered, then was awaken"....? Tricky... that's my 2 cents, maybe only worth that much! ;0)

Awaken can be transitive or intransitive. The opposite of the transitive verb, as in "I awakened you" would be lull to sleep. "I lulled you to sleep." The opposite of the intransitive version, "You awakened" is to fall asleep- "You fell asleep." Its not really that hard; don't we use these terms almost daily? Though i usually say "I woke up" rather than "I awakened," which seems a little precious and not what i would teach my esl students.

It seems there are no one-word antonyms for awaken. Slumber means to be asleep, and lull means to send to sleep. Informally, you could use "crash," as in, "Can I crash at your place?" But "fall asleep" is the term everyone uses. Besides, wake up is more common than awaken.

the antonym of transitive awaken is put to sleep. the antonym of intransitive awaken is fall asleep. that's all there is; but I love some of the made-up words in these comments, my favorite is sleepen. very creative! g2g now, it's time to sleepen my little ones.

We "fall asleep," so we should "rise awake," right? We "go to sleep" and "come awake," right? And "we get up, stand up, stand up for our rights," so we should "get down, sit down, sit down against our restrictions," no?

I just wrote a poem using the word aslumber, not fully realizing that it wasn't a real word as it fit the bill. It would be nice to say that this happened because I'm an ace Scrabble player and used to bluffing, but it just isn't so. I really like the poem, but can't show it to anyone who is a serious poet as they will be all over that word. I have found that poets challenge much more often than Scrabble players and I am growing more and more fond of the word. I guess you could say that Buddhists are awake and everyone else is aslumber.

@Jasper ... If yu are going to borrow the German word and englishen it a bit, it would be inshlafen. To calque it would be insleep or maybe insleepen ... and someone has thought of that: http://www.insleep.com/index2.html

Well, it provides a 'verbification' format like ennoble (from, the noun, noble) which allows to get a new word for sleep also: slaf. Although it wasn't my intention to do that, it works. And plus, I don't like the look of inslaffen, so I dropped the i and used the beginning e.